Do not engage IAuthSecret when running a GSI.

The GSI is not the device owner (it has a separate userdata partition
that can have a separate PIN), and therefore, it should not take part in
anything AuthSecret related.

Bug: 123716647
Test: atest SyntheticPasswordTests
Test: atest LockSettingsServiceTests
Test: PIN unlocks device after booting into GSI
Change-Id: Ide06fc17f91410c562113c0db9a9a08b914b2c4e